A Study on Polymer Binders for High-Capacity Silicon Anode: Effect of Prelithiation Precursors

Abstract

While lithium-ion batteries (LIBs) have advanced and are widely used, increasing energy density remains a significant challenge. Silicon (Si) has attracted attention as a next-generation LIB anode material satisfying high energy density due to its high theoretical capacity. However, volume expansion of Si during repeated Li alloying and dealloying results in low Coulombic efficiency (CE) and short cycle life, posing challenges for integrating into next-generation LIBs. Herein, the role of anionic species in modulating poly(acrylic acid) (PAA) binder performance through systematic comparison of various lithium salts such as OH-, Cl-, and is investigated. The findings reveal that only LiOH treatment achieves authentic carboxylate prelithiation, establishing optimal electrostatic repulsion and chain entanglement balance that facilitates uniform slurry dispersion and enhanced electrode stability. The optimized Si anode with prelithiated PAA binders exhibits a high initial CE and a stable capacity retention. In contrast, LiCl exhibits intermediate chain-extending capacity, forming loosely aggregated microflocs that impair Si electrode uniformity, whereas Li2SO4 induces extensive polymer aggregation, leading to poor dispersion and rapid performance deterioration. These results demonstrate that strategic selection of lithium salts based on their anion-specific effects on polymer architecture represents a promising approach for developing high-performance Si-based anodes in next-generation LIBs.